A monkey wrench can be adjusted to a spacing between a fixed jaw and a movable jaw corresponding to a width-across-flats size of an object to be sandwiched (such as a bolt and a nut). Thus, the monkey wrench is widely used as a convenient tool. On the contrary, since the spacing (hereinafter referred to as “the tool width-across-flats size”) between the fixed jaw and the movable jaw is adjusted by a space adjusting mechanism that is constituted by a worm gear, the tool width-across-flats size is likely to change during a fastening or loosening operation. Accordingly, a corner portion of a hexagonal shape of the bolt or the nut is likely to be rounded. Further, the monkey wrench cannot often sandwich a bolt and a nut that each have even the same width-across-flats size. Thus, readjustment of the tool width-across-flats size is frequently required.
Therefore, for example, Patent Literatures 1 to 4 disclose a mechanism that locks (fixes) rotation of the worm gear in any position. Patent Literatures 5 and 6 disclose a mechanism that reduces looseness (rattling) of a worm gear. These techniques reduce changes in the tool width-across-flats size during the fastening or loosening operation.
Regarding the monkey wrench, in the case where a different bolt or a different nut is used as a target, a worker needs to adjust the tool width-across-flats size corresponding to the bolt or the nut. This operation is troublesome for the worker. In this respect, as disclosed in Patent Literatures 7 and 8, an index scale that indicates a diameter of the target bolt is disposed on the tool. Additionally, the index scale is read to facilitate the adjustment operation of the tool width-across-flats size, as a known technique. These techniques of Patent Literatures 7 and 8, unlike the techniques of Patent Literatures 1 to 6, cannot reduce the change in the tool width-across-flats size.
As techniques that ensure the compatibility with reduction of the change in the tool width-across-flats size and facilitate the adjustment operation for the tool width-across-flats size, Patent Literatures 9 to 11 disclose techniques using ball plungers. With these techniques, for example, a ball of the ball plunger disposed at a movable jaw fits each of a plurality of notches depressed on a sliding surface of a wrench body. Simultaneously, the movable jaw is moved. This facilitates adjustment of the tool width-across-flats size and prevents a change (difference) in the width-across-flats size.
Patent Literature 12 discloses the following technique. In a leaf spring portion, a base end side is firmly fixed to a side surface of a movable jaw while a distal end side is disposed facing a side surface of a wrench body. The leaf spring portion is formed as a leaf spring that is elastically deformable in a contact and separation direction with respect to the side surface of wrench body, and disposed on one side surface and the other side surface of the movable jaw.